In-cylinder air injection via dual-fuel injector

Abstract

A fueling system is provided, comprising: a pressurized air source; a liquid fuel source; a dual injector coupled to the pressurized air source and the liquid fuel source, the dual injector being mounted to inject pressurized air from the pressurized air source and liquid fuel from the liquid fuel source into a combustion chamber of an engine cylinder; and a controller in communication with the dual injector, the controller being configured to cause the dual injector to inject pressurized air directly into the combustion chamber.

We claim: 
     
         1 . A fueling system, comprising:
 a pressurized air source;   a liquid fuel source;   a dual injector coupled to the pressurized air source and the liquid fuel source, the dual injector being mounted to directly inject pressurized air from the pressurized air source and liquid fuel from the liquid fuel source into a combustion chamber of an engine cylinder; and   a controller in communication with the dual injector, the controller being configured to cause the dual injector to inject pressurized air directly into the combustion chamber to achieve a desired air/fuel ratio.   
     
     
         2 . The system of  claim 1 , wherein the pressurized air source is a pressurized air tank of a heavy-duty truck. 
     
     
         3 . The system of  claim 1 , wherein the controller is further configured to:
 receive a throttle input indicating a transient engine condition;   determine a required injection quantity of fuel for the cylinder in response to the received throttle input;   determine an amount of air available to the cylinder via an intake valve configured to control intake air to the cylinder;   determine whether the amount of available air is sufficient to provide a desired air/fuel ratio to the cylinder to improve emissions;   respond to a determination that the amount of available air is insufficient to provide the desired air/fuel ratio by determining an amount of additional pressurized air required to provide the desired air/fuel ratio; and   control the dual injector to inject the additional pressurized air directly into the combustion chamber to provide the desired air/fuel ratio.   
     
     
         4 . The system of  claim 1 , wherein the controller is further configured to:
 determine an amount of torque provided by each cylinder of a multi-cylinder engine;   determine a nominal fuel injection for each cylinder for an engine cycle;   determine for each cylinder a nominal amount of air available to the cylinder via an intake valve coupled to the cylinder for the engine cycle;   determine for each cylinder an air/fuel ratio for the engine cycle to balance the drive torque provided by the cylinders; and   control a dual injector for each cylinder to inject pressurized air into each cylinder as needed to provide the air/fuel ratio for the cylinder to balance the drive torque provided by the cylinders.   
     
     
         5 . The system of  claim 1 , wherein the dual injector is configured to provide at least about three percent of a total air flow to the combustion chamber. 
     
     
         6 . The system of  claim 1 , further comprising:
 a valve coupled between the dual injector and the pressurized air source and a gaseous fuel source, the valve being movable between an air source position wherein the pressurized air source is in fluid communication with the dual injector and a fuel source position wherein the gaseous fuel source is in fluid communication with the dual injector;   wherein the controller is in communication with the valve, the controller being configured to cause the valve to move between the air source position and the fuel source position, to control the dual injector to inject pressurized air into the combustion chamber when the valve is in the air source position and to control the dual injector to inject gaseous fuel into the combustion chamber when the valve is in the fuel source position.   
     
     
         7 . A method of diluting an EGR percentage in an engine cylinder, comprising:
 determining a desired EGR percentage to be provided to the cylinder by an EGR system;   determining a nominal fuel injection for an engine cycle;   determining a nominal amount of air available to the cylinder via an intake valve coupled to the cylinder for the engine cycle;   determining a required amount of pressurized air needed to achieve the desired EGR percentage; and   controlling a dual injector to inject the amount of pressurized air into the cylinder to achieve the desired EGR percentage.   
     
     
         8 . The method of  claim 7 , wherein the dual injector is configured to provide at least about 15 percent of a total air flow to the cylinder. 
     
     
         9 . A method of diluting an EGR percentage in an engine cylinder, comprising:
 determining a fixed EGR percentage provided to the cylinder by an EGR system;   determining whether the fixed EGR percentage is greater than a desired EGR percentage; and   responding to the fixed EGR percentage being greater than the desired EGR percentage by causing a dual injector to inject a quantity of compressed air into the cylinder to dilute the fixed EGR percentage.   
     
     
         10 . The method of  claim 9 , wherein the dual injector is configured to provide at least about 15 percent of a total air flow to the cylinder. 
     
     
         11 . A fueling system, comprising:
 a pressurized air source;   a liquid fuel source;   a dual injector coupled to the pressurized air source and the liquid fuel source, the dual injector being mounted to inject pressurized air from the pressurized air source and liquid fuel from the liquid fuel source into a combustion pre-chamber in flow communication with an engine cylinder; and   a controller in communication with the dual injector, the controller being configured to cause the dual injector to inject pressurized air into the combustion pre-chamber to enhance flame propagation to a main combustion chamber of the cylinder.   
     
     
         12 . The system of  claim 11 , wherein the dual injector is configured to provide at least about five percent of a total air flow to the main combustion chamber. 
     
     
         13 . A fueling system, comprising:
 a pressurized air source;   a liquid fuel source;   a dual injector coupled to the pressurized air source, the dual injector being mounted to inject pressurized air from the pressurized air source into an intake port of a cylinder an engine; and   a controller in communication with the dual injector, the controller being configured to cause the dual injector to inject pressurized air into the intake port.   
     
     
         14 . The system of  claim 13 , further comprising:
 a fuel injector coupled to a liquid fuel source, the controller being in communication with the fuel injector and configured to cause the fuel injector to inject liquid fuel into a combustion chamber of the cylinder.   
     
     
         15 . The system of  claim 13 , wherein the dual injector is further coupled to a gaseous fuel source, the controller being configured to cause the dual injector to inject gaseous fuel into the intake port.